That doesn't mean that magnesium is unimportant in the brain. Au contraire! In fact, there is an intriguing article entitled Rapid recovery from major depression using magnesium treatment, published in Medical Hypothesis in 2006. Medical Hypothesis seems like a great way to get rampant (but referenced) speculation into the PubMed database. Fortunately, I don't need to publish in Medical Hypothesis, as I can engage in such speculation in my blog, readily accessible to Google. Anyway, this article was written by George and Karen Eby, who seem to run a nutrition research facility out of an office warehouse in Austin, Texas - and it has a lot of interesting information about our essential mineral magnesium.

Magnesium is an old home remedy for all that ails you, including "anxiety, apathy, depression, headaches, insecurity, irritability, restlessness, talkativeness, and sulkiness." In 1968, Wacker and Parisi reported that magnesium deficiency could cause depression, behavioral disturbances, headaches, muscle cramps, seizures, ataxia, psychosis, and irritability - all reversible with magnesium repletion.

Stress is the bad guy here, in addition to our woeful magnesium deficient diets. As is the case with other minerals such as zinc, stress causes us to waste our magnesium like crazy - I'll explain a bit more about why we do that in a minute.

Let's look at Eby's case studies from his paper:

A 59 y/o "hypomanic-depressive male", with a long history of treatable mild depression, developed anxiety, suicidal thoughts, and insomnia after a year of extreme personal stress and bad diet ("fast food"). Lithium and a number of antidepressants did nothing for him. 300mg magnesium glycinate (and later taurinate) was given with every meal. His sleep was immediately restored, and his anxiety and depression were greatly reduced, though he sometimes needed to wake up in the middle of the night to take a magnesium pill to keep his "feeling of wellness." A 500mg calcium pill would cause depression within one hour, extinguished by the ingestion of 400mg magnesium.

A 23 year-old woman with a previous traumatic brain injury became depressed after extreme stress with work, a diet of fast food, "constant noise," and poor academic performance. After one week of magnesium treatment, she became free of depression, and her short term memory and IQ returned.

A 35 year-old woman with a history of post-partum depression was pregnant with her fourth child. She took 200mg magnesium glycinate with each meal. She did not develop any complications of pregnancy and did not have depression with her fourth child, who was "healthy, full weight, and quiet."

A 40 year-old "irritable, anxious, extremely talkative, moderately depressed" smoking, alchohol-drinking, cocaine using male took 125mg magnesium taurinate at each meal and bedtime, and found his symptoms were gone within a week, and his cravings for tobacco, cocaine, and alcohol disappeared. His "ravenous appetite was supressed, and ... beneficial weight loss ensued."

Eby has the same question about the history of depression that I do - why is depression increasing? His answer is magnesium deficiency. Prior to the development of widespread grain refining capability, whole grains were a decent source of magnesium (though phytic acid in grains will bind minerals such as magnesium, so the amount you eat in whole grains will generally be more than the amount you absorb). Average American intake in 1905 was 400mg daily, and only 1% of Americans had depression prior to the age of 75. In 1955, white bread (nearly devoid of magnesium) was the norm, and 6% of Americans had depression before the age of 24. In addition, eating too much calcium interferes with the absorption of magnesium, setting the stage for magnesium deficiency.

Beyond Eby's interesting set of case studies are a number of other studies linking the effects of this mineral to mental health and the stress response system. When you start to untangle the effects of magnesium in the nervous system, you touch upon nearly every single biological mechanism for depression. The epidemiological studies (1) and some controlled trials (2)(3) seem to confirm that most of us are at least moderately deficient in magnesium. The animal models are promising (4). If you have healthy kidneys, magnesium supplementation is safe and generally well-tolerated (up to a point)(5), and many of the formulations are quite inexpensive. Yet there is a woeful lack of well-designed, decent-sized randomized controlled trials for using magnesium supplementation as a treatment or even adjunctive treatment for various psychiatric disorders.

Let's look at the mechanisms first. Magnesium hangs out in the synapse between two neurons along with calcium and glutamate. If you recall, calcium and glutamate are excitatory, and in excess, toxic. They activate the NMDA receptor. Magnesium can sit on the NMDA receptor without activating it, like a guard at the gate. Therefore, if we are deficient in magnesium, there's no guard. Calcium and glutamate can activate the receptor like there is no tomorrow. In the long term, this damages the neurons, eventually leading to cell death. In the brain, that is not an easy situation to reverse or remedy.